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See the spill from space

An airplane, visible at top left, flies above the oil spill in the Gulf of Mexico after anexplosion at the Transocean Deepwater Horizon drilling platform. This image was taken from space on April 26 by DigitalGlobe's QuickBird satellte. Click on theimage for a wider, high-resolution view of the scene.

The massive oil spill in the Gulf of Mexico is being tracked from outer space, where the sea's ugly slick takes on a strange kind of beauty.

Ever since the Deepwater Horizon drilling rig exploded on April 20, the National Oceanic and Atmospheric Administration has been analyzing satellite imagery to help figure out how far the spill has spread, and where it's likely to go next. The best projections suggest that oil will reach the Mississippi River delta as early as tonight. For the latest from NOAA, check out the agency's Incident News Web site, which includes maps of the oil spill's "footprint."

NASA provided this April 29 picture of the slick, as seen by the Terra satellite's Moderate Resolution Imaging Spectrometer, or MODIS:

NASA

An instrument on NASA's Terra satellite captured this view of the oil slick off in the Gulf of Mexico on April 29. Click on the picture for a larger view from NASA.

Terra and its satellite sibling, Aqua, circle Earth in a nearly pole-to-pole orbit at an altitude of 438 miles (705 kilometers). Under typical conditions, it would be tough to spot an oil slick in visible light from outer space, because the sheen of oil darkens the blue ocean background only slightly. But the slick shows up as a bright swirl in the image above because Terra made its observations from just the right angle, during a time when sunlight was glinting brightly off the oil.

For more NASA satellite imagery of the oil spill, click through the roundup at the agency's Earth Observatory Web site.

Radar instruments provide a more reliable method to spot spills from space, and that's where the European Space Agency's Envisat satellite came into play, as seen below:

ESA

The European Space Agency's Envisat satellite used its radar-imaging instrument toget this view of the oil spill on April 26. Click on the image for a larger view.

Envisat is following the spill from an orbital height of about 500 miles (800 kilometers) - using its Advanced Synthetic Aperture Radar (ASAR) as well as its Medium Resolution Imaging Spectrometer (MERIS).

Neither clouds nor darkness hinder the radar imager, because ASAR provides its own "illumination" in the form of long-wavelength radar transmissions. But because the radar signals are in only one wavelength, the resulting imagery is in black-and-white instead of color. Check out this Envisat FAQ for more about how radar imaging works.

Eumetsat, the European clearinghouse for meteorological and climate data from satellites, is also on the case. Here's an image from MetOp-A, a weather eye in the sky that orbits from pole to pole. The satellite's imager picks up on spectral differences in the radiation reflected by sea and land - which explains why the color-coded picture doesn't reflect real-life hues:

Eumetsat

A color-coded image from Eumetsat's MetOp-A weather satellite from April 29 showsthe oil spill near the Mississippi River delta. Click on the image for a larger version.

Commercial satellites are contributing images to the cause as well. DigitalGlobe's QuickBird satellite has been keeping track of the Gulf of Mexico spill from a height of 280 miles (450 kilometers). The oil sheen glints in shades ranging from red to green and blue in pictures with enough resolution (2.4 meters per pixel) to make out planes and boats passing through. For more DigitalGlobe imagery, check out the company's Flickr gallery.

DigitalGlobe

The oil sheen from the Transocean Deepwater spill shines in rainbow colors as ships pass through, as seen in this image from DigitalGlobe's QuickBird satellite.Click on the picture for another perspective from msnbc.com's Photoblog.

For more oil-spill imagery, click through our slideshow. And for additional background about the high-tech methods being used to fight the spill, check out these Web reports: